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Show PROBLEMS, SOLUTIONS AND LESSONS LEARNED During the 14-week operation of the modified system, a number of problems were encountered. An overall system availability of 53% was achieved. The factors that account for the 47% unavailability and their proportion are presented in Tables 5 and 6. Table 5 shows that out of 47%, about 7% was due to delays related to testing. The next major cause of the unavailability was the feed characteristics. Both kiln slagging and feed system jamming were a direct result of the excessive plastic, rubber and other trash in the wastes materials. The unavailability due to maintenance primarily represents the downtime during the demister installation. Thus, if the testing delays, maintenance time and downtimes exclusively due to feed characteristics were discounted, the system availability would be more than 70% for relatively trash-free soils. A discussion of the major problems encountered, solutions adopted and lesson learned from these experiences is presented below. o Kiln Problems due to Feed Characteristics The nature of the feedstock presented several restrictions and caused several problems: The presence of combustibles providing more than 1000-1500 Btu/1b would cause kiln overheating (resulting in slagging) and thus limit throughput. The nature of the combustibles present in the feed caused slagging of the kiln walls with a lava-type refractory material that eventually built a dam restricting the flow of material through the kiln. The materials conducive to the slagging were plastic materials used to contain the contaminated dirt during transport to the site, the discarded clothing and material used during clean-up, such as, rubber gloves, plastic suit material, boots, etc. The presence of excessive water in the contaminated soil caused the feed to become muddy and stick to the conveyor belt, weigh scale, and ram trough. The resulting buildup would periodically plug one or the other part of the feed system thus reducing overall feed rates. Occasionally, these blockages caused significant downtime. Although the feed system had trouble processing muddy soil, the kiln operated well with it. Due to the cooling effect of the water, the kiln was able to process increased quantities of high Btu material (plastics, paper, etc.) with reduced slagging. However, feed system problems cancelled much of this advantage. |
